The present invention relates to absorbent articles such as sanitary napkins, catamenials or adult incontinence inserts which are used in combination with undergarments. The absorbent articles according to the present invention have a minimum length of 255 mm, i.e. they are relatively long absorbent articles, and they are provided with a fastening adhesive to attach them to the undergarment during use. In particular the present invention relates to such absorbent articles which are made from several layers which are joined to each other by integrating adhesive connections. A fastening adhesive is provided with an asymmetry in respect to the longitudinal direction and at least one of the integrating adhesive connections is at least co-extensive with the fastening adhesive.
Fastening adhesive for sanitary napkins are well-known in the art. Usually they cover part of the garment facing surface of sanitary napkins. The adhesive allows improved fixation of the napkins to the undergarment when applying the product and during use.
The dimensions of such panty fastening adhesives are influenced by several factors. One aspect is that they should cover as large an area as possible in order to provide firm attachment of the napkin to the undergarment. On the other hand the adhesive must not extend to areas which could possibly attach to the skin of the wearer since that would cause an unacceptable discomfort when using the product. Therefore, when considering the crotch portion of an undergarment typically products having been provided with an adhesive along the longitudinal length of the sanitary napkin such that the adhesive cannot extend beyond the smallest crotch width of the undergarment minus a certain safety margin to allow variation in placement of the napkin in the undergarment depending on user accuracy.
The other aspect when deciding on the panty fastening adhesive dimensions is how to provide the panty fastening adhesive onto the garment facing surface of a sanitary napkin in a mass production process. Many processes have been considered in this respect. EP-A-745 386 discloses printing of panty fastening adhesives in order to allow any shape of panty fastening adhesives to be provided. However, it is still most common to provide panty fastening adhesives by continuous coating or continuous spraying. The panty fastening adhesive is applied while the sanitary napkin moves on a band or belt in longitudinal direction. This automatically results in straight adhesive dimensions, which, when combined with an on-off switching of the adhesive application system, creates a rectangular stripe, or a series of rectangular stripes, on the garment facing surface of a sanitary napkin. By default these stripes cannot reach into a region of the sanitary napkin which extends beyond the smallest transverse dimension, i.e. width, of a sanitary napkin. In practical terms the adhesive needs to be even smaller in order to not extend to the peripheral edges of the sanitary napkin in the crotch region since this is also known to cause problems in comfort for the user, compare for example WO 92/04000. In U.S. Pat. No. 4,690,680 a rectangular adhesive design is suggested in which the adhesive is wider in the front and rear of the article and less wide in the center.
Hence it has become usual to provide sanitary napkins with a single or multitude of rectangular longitudinal stripes of panty fastening adhesive on their garment facing surface. This is acceptable for relatively short sanitary napkins of less than 255 mm, typically of less 240 mm. However, sanitary napkins extending along a larger length also are exposed to more variation in the forces they are exerted to (e.g. they extend from the crotch region beyond the public mons or beyond the anus into the buttocks region) and hence would benefit from better fixation to the undergarment, especially at the ends.
Another reason for not exceeding a maximum width in the crotch area of a panty fastening adhesive (even if a sanitary napkin would allow to provide an adhesive area wider than this certain width) is that the crotch width of undergarments is limited and hence providing adhesive beyond this crotch width is not useful but rather counter productive since it may expose adhesive to the skin of the wearer. This, however, is not the case outside the crotch region of the undergarment where the undergarment flares out into the front portion and into the rear portion covering the buttocks.
Based on the above an objective of the present invention is to provide long sanitary napkins, and in particular those which are asymmetrically shaped, i.e. having a longer and/or wider front or rear portion with a better attachment to the undergarment without violating the fundamental conditions of comfort (i.e. not extending beyond the crotch width of the undergarment with the adhesive) and manufacturing simplicity, for example by use of adhesive coating or spraying with no more variation than an on/off-switching mechanism.
The above has lead to the development of a panty fastening adhesive which is wider in one of the front or rear portion than in the center as disclosed in European application 97119753. This creates however another problem namely that the transmission of forces internally between the layers of the article needs to be sufficient to hold the whole article in place at least across the panty facing adhesive region. This is now achieved by the means of the present invention.
The present invention relates to absorbent articles such as a sanitary napkin for use in an undergarment having a garment facing surface and having a longitudinal centerline and a transverse centerline perpendicular to the longitudinal centerline which define a longitudinal direction and a transverse direction. The sanitary napkin comprises 3 regions, a first region in the center which has a length of at least 40 mm to cover the area on a wearer between the perineum and the most forward point of the labia majora during use. A second region extends in longitudinal direction on one side of the first region and a third region which extends on the opposite side of the first region. The second region is preferably longer than the third region such that the sanitary napkin is worn in an asymmetric fashion. The length in longitudinal direction of the sanitary napkin is at least 255 mm, preferably 270 mm and most preferably 300 mm or more.
The garment facing surface of the sanitary napkin comprises an adhesive for attachment of the sanitary napkin to an undergarment. The adhesive extends from the second region through the first region into the third region and has a width dimension in transverse direction at least in one point of the second region which is larger than the width in either the first or the third region. More particularly the adhesive in the first and third region is provided in a rectangular pattern relative to the centerlines and has a width in transverse direction between 35 and 60 mm while the adhesive in at least one point of the second region has a width in transverse direction of more than the width in the first and second region, preferably in the range 45 to 100 mm. In an even more preferable embodiment the adhesive in the second region is also rectangular relative to the centerlines.
The absorbent article comprises at least three components a generally liquid permeable topsheet, a generally liquid impermeable backsheet, and an absorbent core between the topsheet and the backsheet. Each of the components of the article has a garment facing surface and a wearer facing surface and at least one of the wearer facing surfaces of the components are joint at least partially by adhesive to the garment facing surface of an immediately adjacent component. This forms an integrating connection between the surfaces which integrating connection remains intact during usual use of the article. In particular according to the present invention at least one of the integrating connections is at least co-extensive with the panty fastening adhesive on the garment facing side of the article. In a preferred embodiment according to the present invention all components from the absorbent core layer to the backsheet are attached to each other with integrating connections which are all at least co-extensive with the fastening adhesive. In an even more preferred embodiment according to the present invention which will provide most controlled attachment of the article to the undergarment all component layers of the article are provided with integrating connections between the layers and all of these integrating connections are at least co-extensive with the panty fastening adhesive.
In another embodiment according to the present invention the absorbent article also comprises wings which are well-known in the art. The wings extend a length of at least 80% of the central first region of the sanitary napkin and preferably extend no more than 20% of the length of the third region into the third region while even more preferable the wings do not extend more than 50% of the length of the second region into the second region.